A radioimmunoassay (RIA) for a human lung tumor-associated antigen (hLTAA) is being used to measure levels of hLTAA in the sera of patients with lung cancer. Elevated levels can be detected in lung cancer sera although high basal levels are found in normal sera. The normal serum inhibitor has been identified as alpha1-antichymotrypsin (alpha1ACT) and is distinct from, but immunogenically related to the hLTAA. A quantitative radial diffusion assay has been developed for alpha1ACT. Using these two assays we have found that most lung cancer sera have elevations in both markers but some have elevated hLTAA and normal alpha1ACT values, indicating the presence of a non cross-reacting hLTAA. Sera from patients with cancers other than lung have elevations of both markers but in every case, a high degree of correlation between the two indicates that only one, alpha1ACT, is being measured in both assays. Another form of hLTAA has been purified which is unrelated to alpha1ACT or any other serum protein. Cell migration inhibition factors (lymphokines) are being studied with an emphasis on the nature of the cell receptor which recognizes them. Fucose appears to be involved and purified preparations are being radiolabeled and bound to the receptor as a first step in the development of a radioreceptor assay for these lymphokines.